1. Field of the Invention
The present invention relates to a combination of a drive power transmission device and a differential gear wherein the drive power transmission device is bodily assembled to the differential gear. It also relates to a method of manufacturing the combination.
2. Discussion of the Related Art
Heretofore, as described in U.S. Pat. No. 6,622,838 B2 to K. Suzuki, there has been known a drive power transmission device, wherein a gear shaft with a drive gear for a differential gear is carried by a differential case to be rotatable on a rotational axis thereof, and a clutch case is secured to the differential case. A main or front housing is rotatably carried in the clutch case, and in a clutch receiving chamber inside the front housing, an inner shaft is carried by means of bearings to be rotatable on the rotational axis. A gear shaft is spline-engaged with the inner shaft. A main clutch, a cam-operated amplifying mechanism, a pilot clutch and the like are arranged within the clutch receiving chamber for selectively drivingly connecting the front housing with the inner shaft. The opening end portion of the front housing is covered with a rear housing. An electromagnet is held by a yoke secured to the differential case and is located at a position which is opposed to the pilot clutch with the rear housing therebetween.
However, in the aforementioned drive power transmission device, the inner shaft is supported by means of the bearings within the clutch receiving chamber which is inside the front housing, and the gear shaft which is provided with the drive gear for the differential gear is inserted into the inner shaft through spline engagement. With this configuration, the drive power transmission device section for controlling the torque transmission to driven wheels through clutch operation is functionally separated at the spline engagement section from the differential gear section for the driven wheels. Thus, such mechanical configuration is advantageous because the sections can be manufactured and tested individually and can be assembled to each other thereafter. However, such mechanical configuration disadvantageously increases the number of the parts and the manufacturing cost and gains the weight.